Conventional refuse route vehicles, which are mostly operated with diesel fuel, are one of the most inefficient vehicles on the road. This vehicle type has the additional economic detriment that diesel fuel is primarily produced from imported foreign oil. During operation, the vehicles are used to pickup household and commercial trash and recyclables across communities, which leave behind some air pollutants (e.g., SOx, NOx, and VOCs) and soot while generating as much as 100 decibels of noise.
Refuse route vehicles that operate on natural gas rather than diesel fuel can have quality of life benefits and benefit vehicle fleet operators. There is also an economic benefit to using natural gas, as use of the primarily domestically produced natural gas increases the nation's energy security. Since natural gas is plentiful within the U.S., it is not only less expensive than diesel fuel, but also reduces the threat of an oil price spike or supply disruptions. Based on U.S. Environmental Protection Agency (EPA) and Department of Energy (DOE) studies, CNG trucks produce 75% lower carbon monoxide emissions, 49% lower nitrogen oxides emissions, 24% lower greenhouse gas emissions, and 95% lower particulate matter emissions than similarly sized diesel trucks.1 Natural gas fueled refuse vehicles also produce approximately 70-80 less decibels inside the vehicle.2 1 http://www.afdc.energy.gov/afdc/vehicles/emissions_natural_gas.html2 Baruch College with Council on the Environment of New York City, “Neighborhood Noise and its Consequences,” December 2004
There are several benefits of using natural gas to power vehicles. For example, natural gas costs are approximately one-third lower than that of gasoline. Natural gas prices have exhibited significant stability compared to oil prices, which makes it easier to plan accurately for long-term costs.
CNG powered refuse route vehicles are currently operational. Typically, these vehicles use 4 or 6 high pressure cylinders, approximately 3,600 psig, to store natural gas. As shown in FIG. 1 for a front load vehicle, vehicle 100 comprises cylinders or tanks 101 that are securely installed at the back end on the roof 102 of the body 107, about 13-13.5 ft from the ground. Cab protector 105 is attached to the front face 109 of body 107. Gas pipelines (not shown), which deliver fuel to the engine and refueling tanks (not shown), and electric wires (not shown) for valve control are routed from the cylinders to the location of the vehicle's engines.
FIG. 1A shows an alternative prior art design. Rear loading vehicle 150 includes rear loading mechanism 152 and tank enclosure 151. Notably, a plurality of CNG tanks (not shown) is installed inside of enclosure 151. Tank enclosure 151 is coupled to front face 154 of vehicle body 155. Due to the height of enclosure 151, which is parallel to roofline 153 of vehicle, additional aerodynamic drag is created when the vehicle is in motion. This reduces overall fuel efficiency in the operation of vehicle 150.
FIG. 1B demonstrates the conventional tank enclosure 151 shown in FIG. 1A. CNG tanks (now shown) are configured to fit inside of enclosure 151. As shown in FIG. 1A, the tank enclosure can be coupled, e.g., bolted, welded, etc., to the front face 154 of vehicle body. Brackets 156 are used to attach enclosure 151 to the body 155b of a refuse vehicle. Access panels 158 are used to allow access to valve mechanisms disposed on one end of each CNG tank. Knob 158a is manipulated to open panels 158. Hinges 158b are used to allow panel 158 to open and close. Vehicle operators may manually manipulate valve mechanism to turn on or off the flow of natural gas from the CNG tanks.
Once installed, the rear portion 159a of the tank enclosure 151 faces the front face 154 of body 155b of vehicle. The front portion 159c is configured to fit above vehicle cab 155a. In this conventional design, tank enclosure 151 prevents falling debris from entering CNG tank apparatus. Entry of debris into CNG tank apparatus could damage or dislodge CNG tanks. A damaged or dislodged tank could lead to catastrophic failure such as vehicle fire. However, as vehicle travels in a forward direction, a strong wind vortex will be formed in the L-shaped space of 159c. Consequently leads to an increased drag resistance so the fuel efficiency is reduced.
There are several detriments associated with this prior art design of CNG tank installations. As the tanks 101 are installed on the roof top 102 of vehicle 100, the high elevation of vehicle 100 increases aerodynamic drag, which increases fuel consumption and creates potentially serious safety concerns. For example, as vehicles travel through communities, under bridges, elevated walkways, trees, telephone and electric power lines, the CNG tanks are exposed to possible contact with these objects. Furthermore, as refuse is picked up by front loader mechanism 104 and raised over cab 108, cap 105, sliding door 106 is slid toward the rear of vehicle 100 and refuse is placed into the body portion 107 of the vehicle. This process often allows waste to wipe into tank area 101. Also, as the engine (not shown) is located near the rear of the cab 108 and the tanks are located on the rear top portion of the body 107, a long and complex gas pipeline route and electric wires are required to run on both sides of the truck for delivery of natural gas, refueling and electrical connection. This complexity greatly increases the cost of installation, maintenance and service.
Consequently, there is a need for a method to design, install and operate the CNG tanks on refuse route vehicles that would prevent the shortcomings of previous designs.